Granular smokeless propellant powders



Nov. 20, 1951 s GORDON ET AL 2,575,871

GRANULAR SMOKELESS PROPELLANT POWDERS Filed Sept. 24, 1947 FIG. 3.

Inventors ll STUART GORDON EDWARD WHITWORTH Attorneys Patented Nov. 20, 1951 Stuart Gordon, Saltcoats, and Edward Whitworth, West Kilbride, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Greatliritain 1 Application September 24, 1947. Serial No. 715,950" In Great Britain December 20, 19416 Thepresent invention is concerned with improvements in or relating to granular smokeless propellant powders based on colloided nit-r:- cel'lulose compositions and is particularly con cerned with the provision of granular smokeless propellent powders as aforesaid for shotgun and rimfire cartridges.

It is well known that in the combustion of propellent explosives the amount of gas evolved in any given time for a given composition depends amongst other factors upon the manner in which the burning-surface area varies as burning proceeds. For the aforesaid uses in the case of powders based on colloided nitrocellulose compositions an extremely thin form of grain .of large surface area would be necessary which leads to certain difficulties of production. To over-' come these difiiculties it has long been the practice in the art to incorporate with the ingredients a solid water soluble substance in a fine state of sub-division, and after colloiding the nitrocellulose and forming the powder grains of the preferred size and shape, to leach out the finely divided water soluble ingredient from the powder grains thus leaving a porous structure throughout the propellent grain and consequently large burning-surface, the degree of porosity being controlled by (a) the amount and (b) the grist of the water soluble solid ingredient. It is also well known that porosity improves the ignitibility of thegrains.

We have now made the discovery that a marked duickening, both as regards ignitibility and rate of evolution of gas, can be produced in a porous colloided smokeless propellent composition in d sc r f ake form y providing it. with at least one burning-surface therethrough, as for ex.- arnple, one'or more radial slots, or a central perioratio'n' with or without one or more radial slots. th eby p rmi n smokeles propellent powders of at least standard ballistic performance tobe produced in the aforesaid manner with less of the finely divided water soluble crystalline ingredients with consequential increased convenience and saving in production.

According to the present'invention, therefore, the granular smokeless propellent powders of porous structure based on colloided nitrocellulose compositions, are characterised in that the powders are provided with at least one burning; surface therethrough, as for example, one or more radial slots or a central perforation with or without one or more radial slots. 7

6 Claims. (Cl. 102--8.8j9.

In the drawings. for ing-nartof the specificai'iiQXl-Ii less perforated disc made in accordance with the invention; 1

Figure 2 "is a radially slotted variation of v s Figure 1;

' Figure 3 is representative of a granular smoke less powder perforated flake;

Figure 4 is a radially slotted variation 3; and

Figure 5 shows as an example the nongeometric arrangement of the powder granules of Figure within-a standard type shotgun shell.

performance.

in the casing 13 of a shotgun shell having the usual head II and cap l2, a powder charge I0 made up of the granules having a porous structure {i and perforations 2 and/or radialslots 3 is randomly packed, above which are placed the usual overpowder cardil, wad 8,, .undershot card I, shot 6, overshot card 5. and theseare in turn held in place by the turnover 4.10? casing 13. T,

v Figure 6 is representative of .a granular smokeless powder flake of this invention having two. radial slots therein; and I" Figure 7 is representative of a granularsmokeless powder perforated flake of this invention having one radial slot extending inwardly to said perforation and a second radial slot extending inwardly and stopping short of said perfora: tion. The following comparative'examples illus'tr to the advantages of the invention.

A granular smokeless propellent powder of porous structure is produced in disc form from; colloided nitrocellulose (-13.25% nitrogen) 100 parts by weight; diphenylamine 1.1 parts by weight, and parts by weight'oi finely divided potassium nitrate in order to provide the re quired deg-rec of porosity for a required ballistic Granular smokeless powders of porous structure throughout in disc form and provided in accordance with the invention. with a central perforation therethrough give substantially the same ignition and ballistic performance when produced from colloided nitrocellulose (13.25% nitrogen) parts by weight, diphenylamine 1.1 parts by weight and potassium nitrate 45-50 parts by weight. Y

The comparative results are set forth in Table 1.

i ure l is representative of. a granular smoke Table 1 Charge Sample Porosity derived from- Cartridge Gun weight, 33 7; rs

' grains Powder in square flake form 65pts.potassiumnitrate 12 bore 2% shotgun 12boreshot- 32 2.69 1,085

(noner-forated ,and nonper 100 parts explocartridge with 1% oz gun. slotte sive base shot load. Powder in disc form (non-perdo "do do 32 2.69 1, 084

forated and non-slotted). Powder in perforated disc form.. 45 pts. potassium nitrate .do do 32 2. 67 1, 080

per 100 parts explosive base. Powder in disc form (non-per- 60 pts. potassium nitrate .410-1r 2 shotgun car- .4107 shot- 2.63 996 forated and non-slotted). per 100 parts explotridge with oz. No. gun.

sive base. 6 shot. Powder in perforated disc form" 40 pts. potassium nitrate do do 10 2. 94 l, 006

per 100 parts explosive base.

There is thus a saving of %-30% in the amount of potassium nitrate used in the production of granular smokeless propellent powders according to the invention. The formation of sparks is also decreased thereby indicating a more complete combustion of the powder grains. Comparative results obtained in .22" rifle with standard .22" rimfire ammunition, show improved ignition characteristics for porous powders in perforated or slotted disc form as compared to complete disc form in loose leed and worn rifles denoted by the characteristic small difference between the velocity obtained in a tight leed, rifle and the velocity in a worn loose leed rifle. These comparative results arev not forth in Table II.

compositions in the form of powder grains each enclosing in addition to its pores a plurality of spaces extending through its entire thickness and defining a plurality of surfaces on which the powder grain may burn outwardly.

5. Granular smokeless propellant powders of a porous structure as set forth in claim 4 wherein one of said spacesis a centrally located perforation and the remaining spaces are radial slots.

6.. Granular smokeless propellant powders of a porous structure as set forth in claim 4 wherein said plurality of spaces extending through its entire thickness are radial slots.

'STUART GORDON.

EDWARD WHIT'VVORTH.

Table II Velocity Charge, Velocity Velocity Sample wt. in tight g g igg difiergrains leed rifle rifle ence Disc pro ellant (non-perforated and non- F. s. F. s. F. 6 slotted 30% porosity 1. 4 1, 186 1, 092 94 Slotted disc propellant 30% porosity. 1. 4 1,192 1, 128 64 j 4 Do 1. 4 1,182 1,124 58 Disc propellant- (non-perforated and nonslotted), 75%porosity 1.0 1,035 947 88 Perforated disc propellant, 75% porosity 1.0 1,028 981 47 Disc propellant (non-perforated and nonslotted), 100% porosity 1.0 1,053 974 79. Perforated disc propellant, 100% porosity. 1. 0 1,062 1, 009 53 Disc propellant (non-perforated and nonslotted). porosity 1. 0 1,046 973 73 Perforated disc propellent, 50% porosity v 1. 0 1,046 988 58 Disc propellant (non-perforated and nonslotted), 75% porosity 1. 0 1,010 947 63 Perforated disc propellant, porosity... 1. 0 1, 028 981 47 said space is a radial slot.

':- 3. Granular smokeless propellant powders ofa porous structure as set forth in claim 1 wherein said space is a centrally located perforation.

4. Granular smokeless propellant powders of a porousstructure based on colloidal nitrocellulose REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 677,527 Maxim July 2,1901 726,901 Gathmann May 5, 1903 751,385 Davis Feb. 2, 1904 802,347 Aspinwall .e Oct. 17,1905 $99,577 Wadsworth Sept. 29, 1908 1,077,320. Walsh Nov. 4, 1913 2,261,630 Regestein Nov. 4, 1941 FOREIGN PATENTS Number Country Date 17,994 Great Britain 1894 

